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Interpretive Summary: Fruit flies destroy hundreds of species of fruits and vegetables and are responsible for trade restrictions wherever they occur. Augmentative biological control is a means of their area-wide control and several species of natural enemies are candidates the mass-rearing and release, either individually or in combinations. The later tactic runs the risk of competition among the parasitoids and scientists at the USDA-ARS, Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida in collaboration with colleagues from the Instituto de Ecologia, Xalapa, Veracruz, Mexico examined the behavior and morphology of two such species, one native to Mexico and the other an imported Asian exotic, for overlaps that would make competition likely. There were indeed many considerable overlaps and it was recommended that the exotic species be released alone because of its greater fecundity. One exception might be high altitude pest populations since the native species is more cold-tolerant.

Technical Abstract: Interactions among multiple natural enemies can enhance or interfere with their impacts on host/ prey populations. Two species of Braconidae are currently considered for augmentative biological control of pestiferous tephritid fruit flies in Mexico, the exotic Diachasmimorpha longicaudata (Ashmead) and the native Doryctobracon crawfordi (Viereck). Since niche overlap and competition could influence the range and effectiveness of these parasitoids were they to be released together, we compared behaviors and morphologies that might influence their access to hosts. These included ovipositor length, diel pattern of oviposition, effect of host instar on development, host range (Anastrepha ludens [Loew], A. obliqua [Macquart], A. serpentina [Wiedemann] and Ceratitis capitata [Wiedemann]), host-depth, foraging sucess in different sized host patches, and effects of super- and multi-parasitism. Intra and interspecific adult interactions on host patches were also observed. There were significant overlaps in ovipositor length, diel patterns of oviposition, preferred host age, and host depth and size. D. crawfordi failed to exploit A. obliqua and C. capitata, while D. longicaudata parasitized all four species. D. longicaudata dominated D. crawfordi in multi-parasitism and was better able to survive superparasitism than its competitor. Our results suggested that simultaneous augmentative release of these two species would result in substantial competition. However, because D. crawfordi is naturally found at greater densities than D. longicaudata at high elevations, perhaps because of greater tolerance for cold temperatures, releases in such areas might yield better results than releases of its otherwise superior competitor.